In eastern Montana, the Bakken Formation is an important source of oil and natural gas. Horizontal drilling and hydraulic fracturing play a critical role in the successful production of Montana's largest oil reservoir. The MBMG provides hydrogeologic and geologic information to individuals, public agencies, and the petroleum industry.

Recently collected data show substantial water-level declines in the Fox Hills–Hell Creek aquifer. In some cases this decline has left ranchers without stock water. Possible causes are being evaluated through a computer-generated groundwater model. The modeling effort will be used to replicate the current conditions and simulate the aquifer’s response to predicted increases in water use.

Water resources in eastern Sheridan County

The MBMG has worked with the U.S. Geological Survey and the U.S. Fish and Wildlife Service documenting impacts of oil development on water resources. The work has documented contamination from water co-produced with hydrocarbons. A Contamination Index (CI) developed by the MBMG over 20 years ago uses field values to determine the ratio of chloride to specific conductance. CI ratios greater than 0.035 typically indicate contamination from water co-produced with hydrocarbons. Recently completed projects have documented wetlands, lakes, and groundwater contaminated by oilfield wastes.